electroluminescence

Electroluminescence is the emission of light by a material as a result of electrical excitation. It occurs when electric current or a strong electric field induces electronic transitions that release photons, typically through radiative recombination of electron–hole pairs in semiconductors or by excitation of luminescent centers in phosphor materials.

In semiconductors, electroluminescence arises when injected electrons and holes recombine in a p-n junction or in engineered structures such as quantum wells, producing light with an energy close to the bandgap. In phosphor-based devices, energetic carriers excite doped luminescent centers within a transparent host matrix; the centers then emit photons as they return to lower energy states. Device efficiency depends on carrier injection balance, the radiative quantum yield of the material, and how effectively light can be extracted from the structure.

Materials and device types include inorganic electroluminescent systems, such as phosphor-coated layers and thin-film electroluminescent panels, as well as semiconductor light-emitting diodes (LEDs) made from materials like GaAs, GaN, and InP, which can emit red, green, blue, and near-UV light. Organic electroluminescence yields light from organic semiconductors, forming organic LEDs (OLEDs) used in displays and lighting. Electroluminescent devices range from small-point emitters to large-area panels and flexible, backlit signage.

History and impact: electroluminescence was first observed in 1907 by H. J. Round in silicon carbide, recognizing light emission under electrical stimulation. Since then, advances in materials and device architectures have enabled practical lighting and display technologies, making electroluminescence central to modern optoelectronics.